I recently acquired a calculator, it's the same model of my very first scientific calculator - alas it's not an HP, but I really wanted to have one back, as the original was thrown away many years ago. It's an ELORG 51, which is the same as the Elektronika MK-51.
The sample I found is in good cosmetic conditions, and it works; but the LCD is "slow". I don't know how to explain exactly, but it sort of looks like each segment takes a long time to become black. It's a little like when batteries get very low, only that in this case, once the segments become black, it's a "bright" black, with good contrast, not faded.
I disassembled the calculator, and the inside is in great shape: no corrosion anywhere and no visible damage. But the only components are the main processor, two things that look like dark red/brown resistors, and a small blue thing with two tiny leads on its side, which could be a capacitor. They are marked R1, R2 and C1 but it's a strange font and I don't know if they're actually Latin characters or cyrillic.
Does anyone know these symptoms? What went wrong in the circuit? Is it fixable?